prussdrv_open open failed when trying to open the PRU

[giuliomoro]

Maybe something wrong with kernel modules? this is a diff between lsmod on the previous 4.4.61(working) and the current 4.4.62 (not working)

$ diff mods-working.sorted mods-not-working.sorted
2,4d1
< arc4                    2192  2
< bluetooth             511098  2
< cfg80211              509824  3 mac80211,wl18xx,wlcore
6,16c3,4
< ip_tables              14546  3 iptable_filter,iptable_mangle,iptable_nat
< iptable_filter          1850  0
< iptable_mangle          1849  0
< iptable_nat             2125  0
< libcomposite           53229  14 usb_f_acm,usb_f_ecm,usb_f_rndis
< mac80211              603653  2 wl18xx,wlcore
< nf_conntrack          108839  3 nf_nat,nf_nat_ipv4,nf_conntrack_ipv4
< nf_conntrack_ipv4      17226  1
< nf_defrag_ipv4          1869  1 nf_conntrack_ipv4
< nf_nat                 18076  1 nf_nat_ipv4
< nf_nat_ipv4             6608  1 iptable_nat
---
> ip_tables              14546  0
> libcomposite           53229  8 usb_f_rndis
20d7
< rfkill                 21235  6 cfg80211,bluetooth
33,35c20
< tilcdc                 31016  0
< u_ether                13682  2 usb_f_ecm,usb_f_rndis
< u_serial               13102  3 usb_f_acm
---
> u_ether                13682  1 usb_f_rndis
39,40d23
< usb_f_acm               8036  2
< usb_f_ecm              10981  2
42,45c25
< wl18xx                 99732  0
< wlcore                227162  1 wl18xx
< wlcore_sdio             8686  0
< x_tables               20194  3 ip_tables,iptable_filter,iptable_mangle
---
> x_tables               20194  1 ip_tables

[LBDonovan]

Seem like that's all networking, wifi and USB, nothing to do with the PRU

[giuliomoro]

@LBDonovan has noticed that /sys/class/uio is empty and

[   10.003507] pruss_uio 4a300000.pruss: No children

and found a workaround (which disables the muxer capelet):

diff --git a/resources/BELA-00A0.dts b/resources/BELA-00A0.dts
index 21d9923..e7232fb 100644
--- a/resources/BELA-00A0.dts
+++ b/resources/BELA-00A0.dts
@@ -70,7 +70,7 @@
                        "gpio2_22", "gpio2_24", "gpio2_23", "gpio2_25", "gpio3_19",

                        /* Misc */
-                       "mcasp0", "pru0", "pru1", "i2c1";
+                       "mcasp0", "i2c1";

        /** Pinmux settings **/
        fragment@0 {
@@ -88,18 +88,6 @@
                                >;
                        };

-                       /* Pin mux for PRU GPIOs for multiplexer capelet */
-                       pru_bela_pins: pinmux_pru_bela_pins {
-                               pinctrl-single,pins = <
-                                       0x0b0 0x25 /* pr1_pru1_pru_r30_4,       P8_41 | MODE5 | OUTPUT_PULLDOWN */
-                                       0x0b4 0x25 /* pr1_pru1_pru_r30_5,       P8_42 | MODE5 | OUTPUT_PULLDOWN */
-                                       0x0ac 0x25 /* pr1_pru1_pru_r30_3,       P8_44 | MODE5 | OUTPUT_PULLDOWN */
-                                       0x0a0 0x25 /* pr1_pru1_pru_r30_0,       P8_45 | MODE5 | OUTPUT_PULLDOWN */
-                                       0x0a4 0x25 /* pr1_pru1_pru_r30_1,       P8_46 | MODE5 | OUTPUT_PULLDOWN */
-                                       0x0a8 0x25 /* pr1_pru1_pru_r30_2,       P8_43 | MODE5 | OUTPUT_PULLDOWN */
-                               >;
-                       };
-
                        /* Pin mux for Bela button */
                        bela_button_pin: pinmux_bela_button_pin {
                                pinctrl-single,pins = <
@@ -170,17 +158,6 @@
                };
        };

-       /** PRU **/
-       fragment@2 {
-               target = <&pruss>;
-               __overlay__ {
-                       pinctrl-names = "default";
-                       pinctrl-0 = <&pru_bela_pins>;
-
-                       status = "okay";
-               };
-       };
-
        /** Bela button **/
        fragment@3 {
                target = <&ocp>;

[giuliomoro]

or this actually suggests to add stuff into that fragment https://groups.google.com/forum/#!topic/beagleboard/T5K3IUvNCyA

[giuliomoro]

So what it does not want is a pinctrl-0 unless you specify some pins there. So this works:

diff --git a/resources/BELA-00A0.dts b/resources/BELA-00A0.dts
index 21d9923..f637415 100644
--- a/resources/BELA-00A0.dts
+++ b/resources/BELA-00A0.dts
@@ -175,7 +175,6 @@
                target = <&pruss>;
                __overlay__ {
                        pinctrl-names = "default";
-                       pinctrl-0 = <&pru_bela_pins>;

                        status = "okay";
                };

though it gives

[   10.053822] pruss_uio 4a300000.pruss: pins are not configured from the driver

(harmless).

[giuliomoro]

Although @henrix points out this means the PRU pins are not muxed, so the muxer (hence the name) capelet would not work with this one.

[giuliomoro]

@LBDonovan this has been tracked down by @henrix to be an issue in the boot order (he tried with different kernel). If you load the old dtbo manually after boot, they load with no issue whatsoever.

[giuliomoro]

that's closed / worked around / sped up by this probably https://github.com/BelaPlatform/Bela/pull/285